Suspension systems for the rear wheels of an automotive vehicle not only must provide sufficient resiliency for attenuating shocks and vibrations sufficiently for the comfort and safety of those using the vehicle, but also such suspension systems must provide for self-adjustive or coordinated positioning of the wheels when subjected to shocks, vibrations, and sliding with the aim of maximizing safety in driving and handling the vehicle. A satisfactory suspension system must be able to respond both safely and rapidly to a great variety of road conditions such as, for example, bumps or potholes acting on one or both wheels, a pothole on one wheel and a bump on the other, rolling, slipping and skidding both individually and when encountered simultaneously with bumps and potholes.
It can be shown that for maximal stability and riding comfort during a high-speed turn it is preferable that the wheels be maintained vertical to the ground plane throughout the turn. Also, it is particularly important for stability and comfort that the rear wheels be maintained mutually parallel and confined to vertical motion relative to the ground plane free of tow-in and tow-out steering effects in the event one of them encounters a bump or a pothole during a turn. All known suspension systems have not been completely satisfactory in maintaining this vertical relationship of the wheels relative to the ground plane throughout speed turns and when encountering road surface imperfections.